With a rapid increase in communications traffic, a licensed spectrum of the third generation partnership project (3GPP) is becoming less and less adequate to provide higher network capacity. In order to improve the utilization of spectrum resources, unlicensed spectrums such as 2.4 GHz and 5 GHz bands may already be used in the related art. These unlicensed spectrums are currently mainly used by wireless fidelity (WiFi), Bluetooth, radar, medical and other systems. In order to use a long term evolution (LTE) standard on unlicensed bands, the 3GPP proposes the concept of licensed assisted access (LAA), which uses the unlicensed spectrums with the help of LTE licensed spectrums. However, the unlicensed spectrums may have two working modes, one mode is a supplemental downlink (SDL) mode, i.e., a downlink only includes a transmission subframe; and the other mode is a time division duplexing (TDD) mode, i.e., an uplink and a downlink both include transmission subframes.
In addition, access technologies, such as a WiFi access technology, used on the unlicensed spectrums have poorer anti-interference capability. To avoid the interference, a lot of anti-interference rules are designed in a WiFi system, such as a carrier sense multiple access/collision detection (CSMA/CA) method. A basic principle of this method is that a WiFi access point (AP) or a terminal must firstly sense and detect whether there is an AP or a terminal that is transmitting/receiving a signaling or data in the vicinity before transmitting a signaling or data. If the AP or the terminal senses and detects that there is the AP or the terminal that is transmitting/receiving the signaling or data in the vicinity, this AP or this terminal continues to sense until it is not sensed. If the AP or the terminal senses and detects that there is no AP or terminal that is transmitting/receiving the signaling or data in the vicinity, a random number is generated as a backoff time. In this backoff time, if the AP or the terminal still does not sense and detect that there is the AP or the terminal that is transmitting/receiving the signaling or data in the vicinity, then after the backoff time is over, the AP or the terminal may start transmitting the signaling or data.
In a LTE network, since good orthogonality guarantees an interference level, uplink and downlink transmissions between a base station and a user do not need to consider whether there is a base station or a user that performs transmission in the vicinity. If the LTE does not consider whether there are other devices that use the unlicensed bands in the vicinity when being used on the unlicensed bands, great interference will be brought to the WiFi device. Since as long as there is a service, the LTE transmits it, without any sensing rules, the WiFi device may not perform transmission when the LTE transmits the service, and as long as transmitting the service by the LTE is completed, a channel idle state may be detected, and the WiFi device may perform the transmission.
Accordingly, when the LTE uses the unlicensed bands, it is necessary to ensure that the LAA may coexist with the related access technologies, such as the WiFi access technology, on a fair and friendly basis. However, there is no listen before talk (LBT) mechanism in the traditional LTE system to avoid collisions. In order to better coexist with the WiFi system, the LTE needs a LBT mechanism. In this way, if the LTE detects that a channel is busy on the unlicensed spectrum, the band may not be occupied. If the LTE detects that the channel is idle, the band may be occupied.
However, the inventor has found through a research that when the unlicensed spectrum is used in a TDD manner in the related art, since uplink and downlink configurations of the conventional TDD are fixed, a ratio of uplink and downlink time slots is inflexible, if downlink data is transmitted, uplink and downlink transitions occur due to the fixed uplink and downlink configurations, the channel resources may be snatched by the WiFi device, and a process for transmitting downlink data may be interrupted frequently. Therefore, the TDD manner in the related art is inflexible in uplink and downlink configurations and low in transmission efficiency.